绝密笔记 | Kubernetes 1.19.0——cronjob - V2CE

玩过Linux系统的童鞋都知道crontab定时任务

实际上cronjob就类似于crontab

[root@vms61 chap8-job]# cat job1.yaml 
apiVersion: batch/v1
kind: Job
metadata:
  name: job1
spec:
 #backoffLimit: 6
 #completions: 1
 #parallelism: 1
  template:
    metadata:
        name: pi
    spec:
      containers:
      - name: hello
        image: busybox
        imagePullPolicy: IfNotPresent
        command: ["sh","-c","echo hello world! ; sleep 10"]
      restartPolicy: Never
[root@vms61 chap8-job]# kubectl apply -f job1.yaml 
job.batch/job1 created
[root@vms61 chap8-job]# kubectl get job
NAME   COMPLETIONS   DURATION   AGE
job1   0/1           3s         4s
[root@vms61 chap8-job]# kubectl get pods
NAME         READY   STATUS    RESTARTS   AGE
job1-wt6v5   1/1     Running   0          7s
[root@vms61 chap8-job]# kubectl get pods
NAME         READY   STATUS    RESTARTS   AGE
job1-wt6v5   1/1     Running   0          12s
[root@vms61 chap8-job]# kubectl get pods
NAME         READY   STATUS      RESTARTS   AGE
job1-wt6v5   0/1     Completed   0          22s
[root@vms61 chap8-job]# kubectl get job
NAME   COMPLETIONS   DURATION   AGE
job1   1/1           11s        33s

如果配置文件中的sh改成一个不存在的比如shxxx，且restartPolicy一直未Never的话那么就会一直创建不了，报ContainerCannotRun，也仍然会一直创建；如果restartPolicy改为OnFailure,那么就会一直重启，RESTARTS会一直增加

所以，

job的restart策略只能是：

Nerver：只要任务没有完成，则是新创建pod运行，直到job完成会产生多个pod

OnFailure：只要pod没有完成，则会重启pod，直到job完成

parallelism: N 一次性运行N个pod

completions: M job结束需要成功运行的Pod个数，即状态为Completed的pod数

backoffLimit: N 如果job失败，则重试几次

这里parallelism的值指的是一次性运行几个pod，这个值不会超过completions的值。

成功运行2个pod结束后并成功创建2个新的直至运行完成


[root@vms61 chap8-job]# cat job1.yaml 
apiVersion: batch/v1
kind: Job
metadata:
  name: job1
spec:
  backoffLimit: 6
  completions: 4
  parallelism: 2
  template:
    metadata:
        name: pi
    spec:
      containers:
      - name: hello
        image: busybox
        imagePullPolicy: IfNotPresent
        command: ["sh","-c","echo hello world! ; sleep 10"]
      restartPolicy: OnFailure
[root@vms61 chap8-job]# kubectl apply -f job1.yaml 
job.batch/job1 created
[root@vms61 chap8-job]# kubectl get pods
NAME         READY   STATUS    RESTARTS   AGE
job1-8fsbc   1/1     Running   0          4s
job1-nlqpl   1/1     Running   0          4s
[root@vms61 chap8-job]# kubectl get pods
NAME         READY   STATUS    RESTARTS   AGE
job1-8fsbc   1/1     Running   0          9s
job1-nlqpl   1/1     Running   0          9s
[root@vms61 chap8-job]# kubectl get pods
NAME         READY   STATUS    RESTARTS   AGE
job1-8fsbc   1/1     Running   0          11s
job1-nlqpl   1/1     Running   0          11s
[root@vms61 chap8-job]# kubectl get pods
NAME         READY   STATUS              RESTARTS   AGE
job1-25g8n   0/1     ContainerCreating   0          0s
job1-8fsbc   0/1     Completed           0          12s
job1-nlqpl   0/1     Completed           0          12s
job1-qmqbr   0/1     ContainerCreating   0          0s
[root@vms61 chap8-job]# kubectl get pods
NAME         READY   STATUS      RESTARTS   AGE
job1-25g8n   1/1     Running     0          6s
job1-8fsbc   0/1     Completed   0          18s
job1-nlqpl   0/1     Completed   0          18s
job1-qmqbr   1/1     Running     0          6s
[root@vms61 chap8-job]# kubectl get pods
NAME         READY   STATUS      RESTARTS   AGE
job1-25g8n   0/1     Completed   0          12s
job1-8fsbc   0/1     Completed   0          24s
job1-nlqpl   0/1     Completed   0          24s
job1-qmqbr   0/1     Completed   0          12s

例子：计算圆周率后200位

现在vms62和vms63下载perl镜像docker pull perl

然后在master上运行

可看出圆周率后200位已计算出

[root@vms61 chap8-job]# kubectl create job job2 --image=perl -- perl -Mbignum=bpi -wle 'print bpi(200)'
job.batch/job2 created
[root@vms61 chap8-job]# kubectl get jobs
NAME   COMPLETIONS   DURATION   AGE
job2   1/1           4s         4s
[root@vms61 chap8-job]# kubectl get pods
NAME         READY   STATUS      RESTARTS   AGE
job2-gggqz   0/1     Completed   0          7s
[root@vms61 chap8-job]# kubectl get pods -w
NAME         READY   STATUS      RESTARTS   AGE
job2-gggqz   0/1     Completed   0          13s
^C[root@vms61 chap8-job]# kubectl logs -f job2-gggqz 
3.1415926535897932384626433832795028841971693993751058209749445923078164062862089986280348253421170679821480865132823066470938446095505822317253594081284811174502841027019385211055596446229489549303820

可以看出每隔一分钟就会创建一个新的pod出来

[root@vms61 chap8-job]# kubectl create cronjob mycronjob1 --image=busybox --schedule="*/1 * * * *" --dry-run=client -o yaml -- date > mycj1.yaml
[root@vms61 chap8-job]# cat mycj1.yaml 
apiVersion: batch/v1beta1
kind: CronJob
metadata:
  creationTimestamp: null
  name: mycronjob1
spec:
  schedule: '*/1 * * * *'
  jobTemplate:
    metadata:
      creationTimestamp: null
      name: mycronjob1
    spec:
      template:
        metadata:
          creationTimestamp: null
        spec:
          containers:
          - command: ["sh","-c","date ; sleep 10"]
            image: busybox
            imagePullPolicy: IfNotPresent
            name: mycronjob1
            resources: {}
          restartPolicy: OnFailure
status: {}
[root@vms61 chap8-job]# kubectl apply -f mycj1.yaml 
cronjob.batch/mycronjob1 created
[root@vms61 chap8-job]# kubectl get pods
No resources found in chap8-job namespace.
[root@vms61 chap8-job]# kubectl get jobs
No resources found in chap8-job namespace.
[root@vms61 chap8-job]# kubectl get pods
NAME                          READY   STATUS    RESTARTS   AGE
mycronjob1-1601805180-4x9qs   1/1     Running   0          2s
[root@vms61 chap8-job]# kubectl get pods
NAME                          READY   STATUS      RESTARTS   AGE
mycronjob1-1601805180-4x9qs   0/1     Completed   0          37s
[root@vms61 chap8-job]# kubectl get pods
NAME                          READY   STATUS              RESTARTS   AGE
mycronjob1-1601805180-4x9qs   0/1     Completed           0          62s
mycronjob1-1601805240-w48dq   0/1     ContainerCreating   0          1s
[root@vms61 chap8-job]# kubectl get pods
NAME                          READY   STATUS      RESTARTS   AGE
mycronjob1-1601805180-4x9qs   0/1     Completed   0          72s
mycronjob1-1601805240-w48dq   0/1     Completed   0          11s